Energy efficiency is one factor that is considered when designing a vehicle, such as a work machine. To improve efficiency, vehicles may be equipped with devices that capture and regenerate energy that would otherwise be wasted during the standard operation of the vehicle. In the case of a work machine, which may be, for example, a wheel loader, a track loader, a backhoe, an excavator, a bulldozer, or another earth moving machine, a device such as an accumulator may be included to capture and regenerate energy in the form of pressurized fluid. For example, the potential energy of an elevated work implement may be captured by directing pressurized fluid that is released from a hydraulic actuator to the accumulator instead of directing the fluid to a tank. The stored pressurized fluid in the accumulator may be used to assist the work machine in a later operation, whereas the energy of the fluid directed to tank would be dissipated. By storing and reusing energy in this manner, the overall efficiency of the work machine may be improved.
Many vehicles utilize internal combustion engines to generate the power required to operate the vehicle. The power generated by the engine may be used to move the vehicle along a desired path. The engine may also provide power for additional functions of the vehicle. For example, in a work machine, the engine may be used to drive a pump and generate the pressurized fluid needed to move a work implement through a work cycle.
One possible use of pressurized fluid stored in an accumulator is to assist in the starting of an internal combustion engine. Typically, a vehicle that has an internal combustion engine also includes a battery that is connected to a starter motor. To start the vehicle, the operator turns a key or depresses a start button, which causes the battery to apply a voltage to the starter motor. The applied voltage energizes the starter motor, which may then rotate a crankshaft of the engine to start moving the pistons and thereby start the engine. However, the starter motors are often subject to heavy use and may require periodic maintenance. This periodic maintenance may result in down time for the work machine. In addition, the failure of a starter motor may result in additional down time for the work machine. Thus, maintenance or failure of a starter motor may result in decreased efficiency of the work machine.
As discussed in U.S. Pat. No. 6,206,656, stored, pressurized fluid may be used to assist in the starting of an internal combustion engine. This may be accomplished by directing the pressurized fluid against each piston in an internal combustion engine to move the pistons and thereby start the engine. However, this type of system will require a complex network of valves and fluid lines to provide pressurized fluid to each piston in the engine, as well as to ensure that the delivery of pressurized fluid is timed to help assist the movement of the pistons instead of opposing movement of the pistons.
The system of the present invention solves one or more of the problems set forth above in efficiently starting an engine.